Sharif Digital Repository

The purpose of this study is to investigate a flapping hydrofoil with semi-active kinematics for energy harvesting and evaluate the effect of different dynamic parameters and structures on its performance. The turbulent flow field with Re = 5 × 105 around a NACA 0015 hydrofoil is simulated by URANS method using commercial software and the dynamics of the oscillating hydrofoil is modeled as a mass-spring-damper set in combination with the fluid solver. The sliding mesh method is used for the pitching motion of the hydrofoil with a reduced frequency of 0.14 in combination with the dynamic mesh method for Transitional motion. Initially, the oscillating hydrofoil was considered as a single... 

Token offerings, one of the new methods of financing in the blockchain industry, have provided startups with significant opportunities. In previous studies, most of the factors that determine the success of an initial offering have been examined, and operational performance has been less studied. In this study, the relationship between environmental, social, and corporate governance activities on operational performance and adoption has been presented. Previous studies have shown that more attention to environmental, social, and corporate issues leads to a higher amount of capital raised in the offering. We also address these issues among crowdfunding platforms, which attract more... 

Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,... 

Behaviour of piled-raft foundation on clayey soils have been analysed and assessed by the numerical methods. In this study; emphasis is made on assessment of the settlement distribution and the decrease of differential and average settlement for piled raft foundation. in these type of foundations adding piles are primarily as settlement reducers. In order to study the behaviour of pile raft foundations, numerical modelling with FLAC 3D have been carried out by using the elastic structural elements encoded in the software. In this modelling, the behaviour of soil is assumed Elastoplasts and was modelled by the Mohr-colomb constitutive medel. In this survey, the effects of different... 

One of the most important variants of classical logic is intuitionistic logic, which has arisen from the contemporary studies in the foundation of mathematics. Suppose we want to investigate the foundation of mathematics from a constructive point of view. For this purpose, we can choose two different ways. The first one is to modify the classical set theory, ZFC, in a way that is valid from a constructive point of view and is enough to formulate constructive mathematics, as well. The second approach, which is somehow different from the first one, is a foundational and dependent codification of the same foundation in a way that completely reflects constructive views.In this work we will... 

Daily price limits are boundaries that regulators impose to control daily volatility in stock market. This paper studies the impact of an imposing price limit in Tehran Stock Exchange. To this end we use all the data about companies which were accepted in stock exchange and fara-stock exchange in 1392.In this year the price limit imposed on companies in stock exchange and fara-stock exchange are 4 and 5 percent respectively. Therefore, to estimate the effect of price limit we use the propensity score matching method and inverse probability weighting.The results indicate no significant differences between returns and trade volume between 4% and 5% price limits, but a significant difference... 

This thesis focuses on the network capacity control problem while, risk-averse criteria is considered for decision making. Network revenue management models have wide applications in various industries such as airlines, hotels, railways, rental halls due to handling multiple resources. All models in the related literature are developed based on risk-neutral criteria. However, in this thesis we consider risk-averse policies for many reasons such as risk reduction, covering fixed costs rather than maximizing revenue, and earning some specific revenue within a specific time period. We apply dynamic programming by adopting two types of utility functions: 1) additive and time-separable utility... 

In recent years, dust storms have turned into one of the most prominence environmental issues, existing in Tehran. The infiltration of dust through west borders has led to significant increase in the concentration of Tehran’s pollutants. The main abroad source of these dusts are deserts located in Middle East. The contribution of Middle East deserts in daily concentration of PM10, without the inclusion of local emission sources, was analyzed in previous studies. In this study, we analyzed the contribution of dust storms, formed in Middle East, in Tehran’s PM10 and PM2.5 concentration, using CMAQ model. Dust periods between 2012 and 2014, was identified using observation data and satellite... 

Copper-based semiconductors have received a great deal of attention due to their high absorption coefficient, direct and adjustable energy gap with stoichiometry, low frequency and toxicity. Multicomponent nanocrystals such as CuInS2, Cu (In, Ga) (S, Se) 2, Cu2ZnSnS4 and Cu2SnS3 (CTS) have been successfully synthesized by colloidal synthesis and have shown application potentials such as energy conversion, photocatalyst, thermoelectric and biomedical. Among these, the CTS ternary semiconductor with p-type conduction is one of the most well-known compounds of group I-IV-VI, which consists of abundant and non-toxic elements. In this research, thin-film solar cells with FTO / TiO2 / In2S3 / CdS... 

Turbulence can distort and corrupt the image in quite a few ways when light from a distance star or another astronomical object enters the Earth's atmosphere. It is inevitable that all images produced by any telescope on ther Earth are blurred by these distortions. Adaptive Optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions: it aims at correcting the deformations of an incoming wavefront by deforming a mirror in order to compensate for the distortion. The research work reported in this thesis presents a solution to the surface shape control problems in a Deformable Mirror system. Our first goal is to derive equations that... 

Today, despite the notable progress in diagnostics and therapeutics, cancer remains the second cause of death worldwide. This rather high mortality rate is often attributed to cancers diagnosed at late stages, including prostate cancer. Among the techniques approved for prostate cancer diagnosis, total or free prostate-specific antigen screening using blood serum samples is the sole method able to detect prostate cancer at an early stage. This test has led to a significant decrease in prostate cancer-related deaths. Nonetheless, it possesses several drawbacks, such as the complex, costly, and time-consuming conventional methods utilized in clinical laboratories to assess the concentration of... 

Modern sensors consist of arrays of detectors specially arranged to enhance precision, capabilities, and field of view (FOV). Sensor arrays can have multiple functionalities such as the simultaneous detection of position and motion. We use a linear sensor model and develop an optimization method to design an array of photodiodes. Our objective function minimizes bias and variance estimations. We introduce a maximum likelihood technique to approximate and determine the bias caused by measurement errors, and verify our theory by statistically complete simulations. We apply our theory to design an optimal sun sensor. The sensor has a predefined conical FOV, and its accuracy is controlled by a... 

Millions of people due to factors such as osteoporosis, aging, sports incidents, and accidents face complications from bone fracture injuries every year. Nitinol shape memory alloy and Gyroid metamaterial have attracted researchers to use them as suitable replacements to fill empty areas of broken bones. In this research, numerical modeling and additive manufacturing were used to take advantage of the special properties of both nitinol and gyroid structures. In the modeling section, finite element modeling of the superelastic effect and the one-way shape memory effect of sheet and solid gyroids in cubic and cylindrical geometries with different porosities were done. As a result of the... 

Spine column is the most important musculoskeletal structures. One of the serious health problems in societies, especially among aged population is osteoporosis. Loss of bone density in bone structures is called osteoporosis which increases the risk of fracture due to a decrease of bone stiffness and bone strength. Spine is the most common sites for osteoporosis-related fractures. Current assessment of osteoporosis status is based on bone densitometry tools like QCT (Quantitative Computed Tomography) or DEXA (Dual Energy X-ray absorptiometry). With these methods it is only possible to estimate density without any consideration the morphology of trabecular making parts like rods and plates.... 

Solving Nematodynamic equations with Lattice Boltzmann method is presented.We have studid the effect of shear flow on the direction of Director in different boundary conditions and different geometries.we simulated the 2D Nematic Fluid in simple shear with tangential and perpendicular anchoring and We saw nonliner effects on velocity profile when the anchoring of Nematic and boundary was perpendicular to the boundary.also we have investigated and presented the effect of shear velocity magnitude on the overall direction of Director.Also the effect of shear flow have studid for the Nematic between two hegzagons  

Zinc oxide(ZnO) nanoparticles have been used in a wide-ranging of applications such as transparent UV protection, medical treatments, light emitting diodes, sensors and photovoltaic cells. Many applications of ZnO nanoparticles could be improved by changing the particle size, shape and morphology. In order to take advantage of the unique size dependent properties observed for ZnO anoparticles, knowledge of how particle growth can be controlled is required. As an alternative to transmittance electron microscopy (TEM), which is already used in the study of size and monodispersity of ZnO nanoparticles during synthesis, we proposed a simple spectrophotometric method coupled with chemometric... 

In this thesis we study an unexpected reverse spiral turn in the final stage of the motion of rolling rings. Equations of motion for rolling rings have been derived in the framework of Newtonian and Lagrangian mechanics, and solved in the presence of air drag forces and torques. The rolling motions of ellipsoids and disks have been used to validate the governing equations of motion. Based on experimental tests, we have found that the center of mass of rings moves in an S-shape trajectory. This is in contrast to spinning disks and coins that follow a spiral path before they stop. To explain this behavior, we included the effect of air drag in the equations of motions and found that the escape... 

Aggregation of membrane proteins plays a determinative role in many biological processes، such as signal transduction, cell division and endocytosis. In the present study, we have investigated the interaction between proteins in vesicles by means of coarse-grained molecular dynamics simulations. In the first step, a number of periodic lipid bilayers were simulated and their physical properties were calculated. Then, bilayers were immersed in water and converted into spherical vesicles via a selforganizing process . Finally two proteins were embedded into the vesicle and the potential of mean force (PMF) respect to the angle between them was obtained using umbrella sampling. This process was... 

Aspect ratio dependant optical properties of silver and gold nanorods is responsible for great attention toward controlling the aspect ratio of this class of the nanostructure for their application in variety of area, such as medical diagnosis, drug delivery, biosensing and treatment. In this research, gold and silver nanorods have been synthesized using chemical reducation and growth based on seed mediated method, which is the newest and one of the best methods with less difficulty for producing silver and gold nanorods. Absorption of the visible light by gold and silver nanorods results in appearing the longitudinal and transverse Plasmon bands in their absorption spectra which is related...